Method for the manufacture of elongated objects of concrete

ABSTRACT

The present invention relates to a method for the manufacture of concrete objects by means of a slidable moulding assembly by feeding a concrete mass down from a movable container onto a support bed and vibrating the concrete for the compression of the concrete. The invention eliminates any risk of fissures in the final object primarily by inserting a reenforcement rod into the mass along with some water through an axial bore in a sleeve guide on the container, after a majority of the compressing or compacting of the mass has occurred. A container-carried rotating screw is used for separating, by means of its threads, the concrete remaining in the container from the concrete in the object being formed.

United States Patent [72] Inventors PerOlot'Jonell [54] METHOD FOR THEMANUFACTURE OF ELONGATED OBJECTS OF CONCRETE 1 Claim, 6 Drawing Figs.

521 u.s.c| 264/70,

25/32, 25/41 R, 25/41 J [51] lnt.Cl B28b 1/08 [50] Field of Search264/70;

Primary Examiner-Robert F. White Assistant ExaminerAllen M. SokalAttorney-Wenderoth, Lind and Ponack ABSTRACT: The present inventionrelates to a method for the manufacture of concrete objects by means ofa slidable moulding assembly by feeding a concrete mass down from amovable container onto a support bed and vibrating the concrete for thecompression of the concrete. The invention eliminates any risk offissures in the final object primarily by inserting a rcenforcement rodinto the mass along with some water through an axial bore in a sleeveguide on the container, after a majority of the compressing orcompacting of the mass has occurred. A container-carried rotating screwis used for separating, by means of its threads, the concrete remainingin the container from the concrete in the object being formed.

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METHOD FOR THE MANUFACTURE OF ELONGATED OBJECTS OF CONCRETE It is knownto manufacture lengthened concrete elements by means of horizontalsliding mould casting. The concrete by this method is fed out through anopening at the lower end of a container and down to a flat bed. Thecontainer with the concrete mixture is moved slowly along the bed.Moving after or trailing behind the container there is arranged a slidehaving a vibrator by means of which the concrete layer, formed on thebed, is vibrated and compressed. The container and the vibration slideare moved with even speed over the bed. The slide with the vibrator willthus move over the concrete fed out of the container and distributedover the bed and compress the concrete. When the concrete leaves theslide with the vibrator, it is finally compressed and need thereafter nosupport moulds. The method requires that the resistance of the concrete,when the latter leaves the slide with the vibrator, the sufficient sothat the object formed retains its shape without sagging or forming offissures. The concrete must be dispensed from the container very evenlyand carefully as otherwise there is obtained an object having variatingproperties concerning resistance, tightness and dimensions. For thispurpose expensive and complicated laying devices must be used. Themethod further requires that the concrete has such a consistency andviscosity during the vibration that the reinforcement when such is usedbe completely enclosed and embedded.

From the container, the concrete must be laid out with a height of H soadjusted that the final object, the beam will have a height H, that isthe correct one. The relation l-l/H is inversely proportional to therelation between the volume weight of the concrete when uncompressed andwhen compressed, respectively. The value of the relation is about0.5-0.69. This means in practice that if one desires to make a beam withthe final height of e.g. 20 centimeters, one has to lay out the concretein front of the vibration slide with a height of about 40 cms. Duringthe vibration the concrete will be displaced vertically downwards whichaction, in particular when there is a question of a manufacture ofrather thin beams standing on one longitudinal edge, is to be consideredas an important drawback and considerably restricts the method. Theconcrete must on the one hand be rather loose to such an extend that itcan completely flow around the reinforcement irons at the displacementdownwards during the compression and on the other hand difficultiesarise for laying out the concrete in the correct amount. Thesedifficulties are further increased with an increasing height and/ordecreasing width of the beam. The limit for the method is at presentprobably situated at beams with a height of about 20 centimeters and awidth of about 5 centimeters. So as to assure that the reinforcement issufficiently embedded in the concrete during the reinforcement it is, asa rule, necessary to lift the reinforcement irons continuously to thesame extent as the concrete is displaced downwards during the vibration.The same is true by the use of a cavity or hole moulder, i.e. by the useof rods usually in the shape of tubes for forming longitudinal holes inthe object formed.

The possibility of making the concrete so loose and fluid that itflows'in the desired way below the slide with the vibrator is restrictedby the requirement of using a rather stiff consistency necessary inorder that the object formed shall retain its form after the compressionand before the hardening of the concrete. From the point of view ofresistance, it is advisable to use a consistency as stiff as possibleand a water content as low as possible. Another factor limiting themethod is the friction between the concrete and the sides of the slidingmould. 1f the height of the sides is too large in relation to the widthof the object formed, the concrete will stick to the sidewalls of themould below the slide with the vibrator, which causes undesirable theformation of cavities and fissures in the final products.

Proposals have been made to overcome said drawbacks and to renderpossible the manufacture, by means of sliding moulding, of lengthenedconcrete objects of considerable height, e.g. -100 cm. and with aminimum thickness of about 4-5 cm. According to one proposal the sidesurfaces of the concrete layer formed on the bed are vibrated directlybelow the container filled by the concrete mass so that the concretemixture is fed from the latter to compensate for volume of concreterequired for the compression obtained by means of the vibration inlateral direction of the concrete layer formed below the container. [tis possible by means of this method to compress directly under thecontainer the concrete layer to about 80-90 percent and perhaps evenmore which thus means that the concrete layer may at the place where theupper surface of the layer is stripped, be laid with a height l-l whichis only by 20-10 percent in excess of the height H of the final element.Thus, the subsequent slide with the vibrator has only to compress theconcrete layer in vertical direction by about 10-5 percent or less whilethe final compression in lateral direction is carried out by means ofthe sidewalls of the mould below the vibration slide. The concrete massis fed or flows down from the container not only to fill the interspacebetween the sidewalls of the sliding mould but also to compensate forthe compression obtained by means of these walls. During the vibrationonly from above of elements shaped as beams, it is not possible toobtain any similar compression effect. First there is obtainedindependently of the height of the element a homogenous compression ofthe element in the direction of its height. Responsive to a compressiononly from above, the element will be incompletely compressed at thelower portion. Otherwise a higher water-cement ratio must be used inorder to obtain a sufficient compression. One can operate with concretehaving a rather low water-cement ratio, i.e. the weight relation betweenthe water and the cement in the concrete mixture. The water-cementration may as a rule be kept as low as about 0.27-0.35 for a cementcontent of about 300-350 kgs. /m. which corresponds to a water contentof about -120 l./m.. Due to this rather low watercement ratio there isobtained a product with a rather high resistance. Another advantage inthis rather dry concrete is to be seen in the prevention of a stickingbetween the side surfaces of the formed object and the sides of themould. The strong vibration makes it possible to use a low cementproportion.

However, because as the concrete layer strongly compressed below theslide mould will have a rather firm consistency, it becomes ratherdifficult for the vibration slide to strip the concrete mass at theupper border of the concrete object. It has resulted in the same burstsand the fissures which extend deeply down into the concrete object. Animportant object of the present invention is to overcome this drawback.According to the invention the concrete layer below the container isseparated from the concrete mass remaining in the container by means ofthe threads of a rotating screw which extends in the longitudinaldirection of the slide mould and is brought along by the latter duringthe advancement. The screw is driven in such direction a way that theconcrete mass is fed rearwards, i.e. in opposite direction to thedirection of advancement of the slide mould preferably in such a waythat the screw is driven rearwards a little faster than the slide mouldis advanced. Thus, there is obtained a certain compression of theconcrete mass in the upper layer before the vibration slide carries outthe vertical vibration. The risk for the formation of fissures in theobject formed is practically eliminated by means of the rearwardsfeeding by the screw.

According to a further embodiment of the invention the reinforcementiron or rod extending in the longitudinal direction which generally isarranged at the upper border of the concrete object being formed, isinserted through an axial bore in the screw during the advancement ofthe slide mould. The reinforcement iron will then leave the bore in thescrew at the rear end of the same, i.e. at a place in the concreteobject formed where the concrete mass already has been compressed toabout 80 percent. By means of the remaining compression of 20 percent ofthe concrete massthis compression being performed essentially by meansof a vibration in lateral direction by the sidewalls of the mould belowthe vibration slide-there does not occur any noticeable displacement ofthe reinforcement iron in the concrete object, so that the reinforcementiron will retain its given position, i.e. get the correct position inthe object, the concrete beam.

The advantage in feeding the reinforcement rod through the screw doesnot reside solely in a correct final position. If the upper borderreinforcement rod is fed before or ahead of the container, thereinforcement rod will be pressed downwards by the descending concrete.In case the reinforcement is not suspended by bows or by beingtensioned, it will eventually slide down to the bottom. On the otherhand, if the reinforcement rod is lifted (as above), it is pressed downby the concrete to such an extend that it rebounds when the finishedbeam leaves the machine. However, this formation of very dangeroushorizontal fissures in the beam. Also, the feeding does not have to becarried out by means of a special tube. The main point is that thefeeding proper takes place after the container when the main compressionalready has been carried out.

However, during vibration the concrete mass and the reinforcement ironwill vibrate independently of each other to a certain extend and this istrue for a vibration by means of the mould walls in a lateral directionas well as the vibration by the vibrating slide in a vertical direction,this vibration having a rearwardly directed reaction force. This causesa risk that the iron will tear up a longitudinally extending cavity inthe concrete mass in which case the result of course, will be aconsiderably reduced effectiveness of the reinforcement iron in theconcrete object. To this end, according to a further aspect of theinvention water is fed around the reinforcement iron into the borewithin the screw at the front end of the same. The screw is inclinedslightly rearwards and the water thus flows from the bore at the rearend of the screw. Thus, the continuous concrete mass is here softened tosuch an extent that it will well embed the reinforcement iron such thatthe strength of the final concrete element is considerably increased.

The method makes it possible to manufacture grooved or channel-shapedconcrete elements, having two parallel and rather high sidewalls bymeans the improved slide moulding as described and which sidewalls areformed continuously on a rather thin concrete layer formed shortlytherebefore, said thin concrete layer being possibly laid out on a bed(e.g. according to the method described in our copending Swedish Pat.application No. 1467/65.)

The invention also relates to a machine for carrying into effect themethod set forth hereinabove, said machine comprising a stand movableover a bed and having one or several containers for holding a concretemixture, said containers having at their lower ends discharge openingsfor the concrete mixture and sidewalls extending ahead of and behind thecontainer for forming the side surfaces of the concrete layer formed onthe bed. At least one of said sidewalls is adapted to be vibrated in alateral direction and includes a device for a vertical vibration of theupper surface of the concrete layer formed. A main feature of theinvention is that at the bottom of the container there is rotated ascrew extending in the displacement direction of the container, saidscrew being adapted, during the slide moulding, by means of its threadsto separate the concrete mass remaining in the container from thelaterally vibrated concrete object already formed.

Further features of the invention will be obvious from the followingdescription with reference to the accompanying diagrammatical drawings,In the drawings:

FIG. 1 shows a vertical longitudinal section through a machine accordingto the invention,

FIG. 2 shows on an enlarged scale a vertical longitudinal section ascrew mounted for rotation in the machine,

FIG. 3 is a partly longitudinally sectioned side elevation of a slidemould assembly for the manufacture of grooved concrete elements,

FIG. 4 is a view from above of the assembly of FIG. 3,

FIG. 5 shows on an enlarged scale a vertical section on line v-v in FIG.3', and

FIG. 6 shows on an even more enlarged scale a similar vertical crosssection through the left-hand part of the aggregate according to FIG. 5.

The moulding machine shown in FIGS. 1-3 comprises a 5 container 1 withan opening 2 at its lower end for the discharge of the concrete mixture3 in the container. The container 2 is carried in a stand 4 (see FIG. 6)with running wheels 5 for the displacement of the machine on a flat bed6. For the forming of the concrete layer or the sides of the concreteobject 7 there are used parallel sidewalls 8 which extend in the forwarddirection as well as in the rearward direction beyond the container 1(see FIG. 1). The machine is further provided with a slide 9 for formingthe upper surface 10 of the object 7. The slide 9 is provided with avibrator 11 for the compression of the concrete layer 7 in verticaldirection. By means of springing means 12 the slide 9 is suspended onthe stand 4 such that it can perform a vibration in a vertical plane.Reference letter 13 denotes a stripper at the rear edge of the opening 2at the container 1. The rear end of the slide 9 is provided with asomewhat resilient steel plate 14 which prevents the concrete layer fromforming a transverse bulge, a so-called pressure bulge at the rear endof the slide.

At least one mould wall 8, preferably the inner one (according to FIG. 6the right hand one) is provided with a vibrator l5 and is by means ofspring means 16 suspended in the stand 4 in such a way that it canvibrate in a horizontal plane. The vibrators l1 and 5 are arranged insuch a way that an obliquely rearward force is applied against the uppersurface and side surfaces 17 of the concrete layer 7 formed. To preventan occurrence of a transverse bulge on the side surfaces 17, due to thevibrations of the sidewalls 8, the walls 8 at their lower ends also areeach provided with their resilient steel plate 18; (FIG. 4). The plates14 and 18 cause, due to the vibration, also a certain so-called steelgrinding of the concrete object 7.

The advancement of the machine along the bed 6 is carried out by meansof an electric motor 19 via a chain 20 to the running wheels 5.

A rearwards and downwards inclining screw 23 is mounted for rotation inthe opening 2 with one end 21 supported in a bearing 22, and the screw23 extending in the longitudinal direction of the stand 4. The screw isdriven by an electric motor 24 via a pair of cogged wheels 25 and 26.Axially extending in the screw is a bore 27 through which areinforcement iron 28 can be moved. Above a receptacle 29, debouching atthe front end of the bore 27 of the screw 23, there is arranged ajetnozzle 31 connected to a pressure water conduit 30, for feeding watervia the bore 27 to the concrete mass at the farmost end 32 of the screw23.

When the machine is displaced in the direction of the arrow 33 accordingto FIG. 1, the rather dry concrete mixture (the water-cement ration ise.g. 0.27-0.30) is fed or slides through the opening 2 down into the bedwherein 6, horizontally or vertically bent reinforcement irons 34 and 35are laid on said bed 6. The space between the sidewalls 8 of the machineis filled with concrete mass from the container 1. Due to the vibration,an intense compression of the concrete slab is obtained in the lateraldirection and a new mass continuously flows down and out of thecontainer to compensate for the concrete mass used up by means of thecompression of the same. Below the stripper 13, where the concreteobject 7 has the height H the object is assumed to have been compressedalready to 90 percent. Further compression of the concrete object iscarried out by means of the walls 8 below the slide 9. This compressionin lateral direction is assumed to be carried out to an additionalpercent. Thus, this means that the height and width dimensions of thecross section of the concrete object below the stripper 13 has to bereduced, by means of compression, by only about percent or less. Thefinal object will be very firm and homogenous. The height H of the samecould for this reason be considerable and the width rather small. Themass already intensely compressed below the container 1 is separatedfrom the remaining concrete mass 3 in the container by means of thethreads on the screw 23 which is driven at such a speed that theconcrete mass by means of the screw threads is displaced in forwarddirection (in the direction of the arrow 33). At the same time areinforcement iron 28 is moved through the bore 27 within the screw 23into the mould. As no further notable compression of the concrete object7 occurs in vertical direction by the slide 9, the reinforcement iron 28will assume the correct distance relative to its upper surface 10, saiddistance 36 being determined by the inclination of the screw 2 and thelevel of the outlet. It might for this reason be advisable to make thebearing 22 for the screw 23 adjustable in such a way that the desiredinclination of the screw 23 is easily obtained.

Due to the water addition through the jet 3] to the concrete mass at therear end 32 of the screw 23, there is obtained the desired higherwater-cement ratio the mass about the reinforcement iron 28.

In FIGS. M there is illustrated the manufacture of a grooved orchannel-shaped object 37 (FIGS. 5-6) made of concrete. This object 37, agrooved beam, has a bottom slab portion 38 and sidewall portions 39extending upwards from the same. The bottom portion 38 is firstmanufactured on the bed 6 and may preferably be produced by a slidemould machine 40 (FIG. 3 to the right) which has been described more indetail in my copending Swedish Patent application No. 1467/65. At thedisplacement of the machine 40 in the direction of the arrow 41 in FIG.3, the rather dry concrete mixture 42, which in this case may have awater-cement ratio as low as about 0.25-0.27, flows through the opening43 in the container 44 down on the bed 6, a downwards inclining slope 45of the concrete mixture then being fonned below the front border 46 ofthe opening. Water is sprayed onto this slope 45 from jets 47 as evenlyas possible. A part of the water then flows down towards the bed 6 wherethus the water-cement ratio in the layer 48 will be as highest. Thusupper surface of the concrete layer is automatically smoothed by thestripper 49. The front border 46 is situated'on a lower level than thestripper 49. The concrete layer is compressed by the aid of the slide 50of the machine 40 thereby that the vibrator 51 of the slide is vibratedwhereby there is obtained the desired density of the layer. By means ofthe compression a part of the water in the layer 48 is pressed upwardssuch that there is obtained a certain equalizing of the water content inthe layer as a whole. The water content at the upper surface, however,never will be as high as to incur any risk that the slide 50 will becomestuck to the layer, thereby assuring that the final bottom slab 38 willhave a smooth, firm layer at the upper surface. The bottom slab will bevery firm and there is no risk whatsoever that it be deformed when thesidewalls 52 of the machine have moved beyond it.

As shown in FIG. 6 the opposed longitudinal sides of the bottom slab 38each provided with an upwardly projecting portion 53 having a heightwhich is say two to three times larger than the thickness of the bottomslab. These upwardly projecting portion 53 form, as shown in detail inFIG. 6, a guide for the walls 8 on the succeeding slide mould machine54, to follow, as shown in FIG. 3.

Immediately upon the compression of the layer 48 there are laid twolayers of concrete by means of containers 1 carried at some distancefrom each other by a common stand 55, said layers being vibrated by thesidewalls 8 and the slides 9 in the way described in the aforegoing withreference to FIGS. 1 and 2. Thus, it is possible, by means of theassembly shown in FIGS. 1 and 2, to manufacture, by means of slide moldcasting, reinforced grooved or channel-shaped beams having a rather thinbottom slab or web portion and rather thin opposed high walls 39. Thisbeam will, in spite of the rather small material consumption, have avery high resistance and supporting abilit Also, the machine 54 for theforming of the objects 7 and the walls 39, respectively, may be providedwith jets 47 (not shown) connected to a water conduit for spraying wateronto the slope 56 of the concrete mass 3 flowing out of the container 1of the machine 54. In such a case there is obtained an enrichment ofwater in the concrete mass near the upper surface of the slab 38 formed,i.e. on the upper surface of the upward longitudinal portions 53 of thebottom slab. At the subsequent vibration and compression of the concretemass by means of the sidewalls 8 and the slides 9 there is obtained anequalizing of the water content in the concrete object formed. In thosecases where the edgewise arranged concrete walls 39 are to be providedwith a reinforcement at the lower border, it is advantageous by such awater spraying of the concrete mass 3 at the front end of the machinethat a good embedding of the concrete mass is ensured around thereinforcement irons during the subsequent vibration.

The invention has been described in the aforegoing for purposes ofillustration only and it is not intended to be limited by thisdescription or otherwise except as defined in the appended claims. Thus,the slide mould machines 40 and 54 may be constructively modified inmany ways within the scope of the inventive idea. The machines 40 and 54may be alternatively moved, instead of on running wheels 5 or carriedalong longitudinal beams or rails mounted in the ceiling of the roomwhere the slide moulding is carried out. The assembly according to theinvention may be used for the manufacture of beams having L- or T-shapedcross section instead of being grooved or U-shaped, and in such a caseone single longitudinal wall 39 is cast on the bottom slab 38.

In case there should be desired or needed, at the upper border of thewalls 39, two reinforcement irons parallel to each other, it might beadvisable to dispose, in the opening 2 of the container 1, two of therotatable screws 23 having the axial bore 27. The reinforcement ironsmay be provided, instead of through a bore in the screw or instead ofusing any screws, by being inserted through or guided down into themould by means of one or several plain tubes; inclining obliquelydownwards and rearwards, and water may be fed to the mouth of saidtubes. I

The problem in connection with the stripping of the concrete masswithout incurring formation of fissures in the object formed-the beam-iseven more pronounced if the beam has a thin web and the latter by meansof a neck continues in a broader portion extending along the upperportion of the beam where the pressure zone proper is situated. In sucha case the retaining forces will be smaller during the formation thanthe ones tending to push the concrete mass in a forward direction forthe reason that the pressure zone is broader than the web. To ensurethat the material in the web in this case is sufficiently compressed andat the same time to prevent the concrete mass from being stuck in theneck, i.e. in the passage from the broader part and the narrower part ofthe beam, the neck must be brought to incline rearwards and downwardsunder the slide 9 as shown in FIG. 1. Due to the use of a feeding screw23 and the rearward inclination of the part of the mould formed by theneck, there is obtained a beam without fissures.

What we claim is:

1. A method for the manufacture of elongated and in particular ratherthin and edgewise arranged reinforced objects made from a fluid concretemixture by means of a slidable moulding assembly comprising: feeding afluid but relatively stiff concrete mass from a continuously advancingcontainer (1) down from above generally vertically onto a bed below saidcontainer; laterally supporting and initially forming said mass whilemainly and initially compressing it in a lateral direction into arelatively rigid layer having generally mutually parallel longitudinalborders, supplementally compressing and smoothing the upper surface ofsaid layer by means of a subsequent compression in vertical directionwhile still laterally supporting same; and inserting a reinforcementiron (28) at the upper border of the object through an axial bore (27)in a sleeve guide (23) carried by and during the advancement of saidcontainer (1); said iron being fed longitudinally from above the levelof the final upper surface of the object being moulded and the ironinserting occurs after the initial main compressing to preclude by saidsubsequent compacting an moulded object to thereby facilitate acompacting of said concrete mass around the reinforcing iron andmaintaining a much stronger and lower concrete-water ratio in theremaining mass of the formed object,

